I Like This New Me: Unravelling Population Structure of Mediterranean Electric Rays and Taxonomic Uncertainties within Torpediniformes.

The present study focused on the three species of electric rays known to occur in the Mediterranean Sea: Torpedo torpedo, Torpedo marmorata and Tetronarce nobiliana. Correct identification of specimens is needed to properly assess the impact of fisheries on populations and species. Unfortunately, torpedoes share high morphological similarities, boosting episodes of field misidentification. In this context, genetic data was used (1) to identify specimens caught during fishing operations, (2) to measure the diversity among and within these species, and (3) to shed light on the possible occurrence of additional hidden species in the investigated area. New and already published sequences of COI and NADH2 mitochondrial genes were analyzed, both at a small scale along the Sardinian coasts (Western Mediterranean) and at a large scale in the whole Mediterranean Sea. High levels of genetic diversity were found in Sardinian populations, being significantly different from other areas of the Eastern Mediterranean Sea due to the biotic and abiotic factors here discussed. Sardinian torpedoes can hence be indicated as priority populations/areas to be protected within the Mediterranean Sea. Moreover, sequence data confirmed that only the three species occur in the investigated area. The application of several 'species-delimitation' methods found evidence of cryptic species in the three species outside the Mediterranean Sea, as well as in other genera/families, suggesting the urgent need for future studies and a comprehensive revision of the order Torpediniformes for its effective conservation.

Morphology of the clasper musculature in rays (Chondrichthyes; Elasmobranchii: Batoidea), with comments on their phylogenetic interrelationships.

The subclass Batoidea comprise skates, electric rays, stingrays, guitarfishes, and sawfishes, and their interrelationships are still problematical despite recent morphological and molecular phylogenetic studies. The most recent morphological phylogeny indicates that guitarfishes are a polyphyletic group, and that the phylogenetic placement of Platyrhina and Platyrhinoidis is still unclear. Several molecular studies suggest that guitarfishes (except Zanobatus) and sawfishes comprise the monophyletic order Rhinopristiformes, and that thornback rays (Platyrhinidae, Platyrhina, and Platyrhinoidis) are more closely related to the electric rays (Torpediniformes); rhinopristiforms have recently been supported by morphological data as well. The clasper musculature of batoids suggests an alternative pattern of interrelationships for thornback rays, with the m. dilatator attached to the dorsal terminal 1 cartilage by a series of tendons found only in Rhinopristiformes and Platyrhinidae, suggesting that they are closely related. Furthermore, Rajiformes, Rhinopristiformes, and Platyrhinidae exclusively share a reduced m. extensor lateralis, suggesting that these taxa form a monophyletic group. This study identifies new synapomorphies that corroborate the separate monophyly of Rajiformes, Torpediniformes, and Myliobatiformes: the m. dilatator divided into dorsal and ventral bundles and the presence of a single m. flexor are found only in Rajiformes; the extensor lateralis with a laminar shape is a derived character of Torpediniformes; and the exclusive m. flexor medialis arising on the puboischiadic bar is derived for Myliobatiformes.

Descripción y comparación de la línea lateral de tres especies de rayas eléctricas del género Narcine (Torpediniformes: Narcinidae) / Description and comparison of the lateral line of three species of electric rays of the genus Narcine (Torpediniformes: Narcinidae)

Resumen Se presenta la descripción de la composición y arreglo estructural del sistema de la línea lateral de tres especies de rayas eléctricas (Narcine bancroftii, N. entemedor y N. vermiculatus). Las tres especies muestran los canales supraorbital (SO), infraorbital (IO), hiomandibular (HYO) y de la línea lateral posterior (LLP), menos ramificados que en otros batoideos. Narcine entemedor difiere de sus congéneres por la gran ramificación de los canales SO e IO, los cuales convergen en la región inter-orbital; en N. vermiculatus estos canales presentan una condición similar, pero con una menor ramificación. En contraste N. bancroftii presenta los canales divergentes (dirigidos hacia afuera de la región inter-orbital). Los canales HYO están localizados en la periferia de los órganos eléctricos en estas especies; en N. bancroftii las ramificaciones se extienden hacia la región posterior, mientras que en las demás especies están reducidas (N. entemedor) o casi ausentes (N. vermiculatus). La LLP es de forma curva y está dirigida hacia el urostilo, asimismo muestra un gran número de ramificaciones, excepto en N. vermiculatus. La información sobre el arreglo y el número de poros sobre el sistema de canales de la LL en Narcine, puede ser de utilidad para la distinción taxonómica de sus especies, tal como ha sido corroborado para otros Torpediniformes.

Abstract This study describes the composition and structural arrangement of the lateral line system of three electric ray species (Narcine bancroftii, N. entemedor and N. vermiculatus). All three species showed the supraorbital (SO), infraorbital (IO), hyomandibular (HYO) and posterior lateral line (PLL) canals, less branched compared to other batoids. Narcine entemedor differs from its congeners by the extensive branching of the SO and IO canals, which converge in the inter-orbital region; in N. vermiculatus these canals present a similar condition, but are less branched. In contrast, N. bancroftii has divergent canals (directed outwards from the inter-orbital region). HYO canals are located on the periphery of the electric organs in these species; in N. bancroftii the branches extend towards the posterior region, whereas in the other species are reduced (N. entemedor) or almost absent (N. vermiculatus). The PLL is curved and projected towards the urostyle, it also shows a large number of ramifications, except in N. vermiculatus. Information about the LL canal system arrangement and pore number in Narcine can be useful for the taxonomic distinction of its species, as it has been corroborated in other Torpediniformes. Rev. Biol. Trop. 66(2): 586-592. Epub 2018 June 01.